Kicked-rotor quantum resonances in position space: Application to situations of experimental interest

In this work we apply the formalism developed in [M. Lepers \emph{et al}., Phys. Rev. A \textbf{77}, 043628 (2008)] to different initial conditions corresponding to systems usually met in real-life experiments, and calculate the observable quantities that can be used to characterize the dynamics of the system. The position space point of view allows highly intuitive pictures of the physics at play.Comment: accepted in Eur. Phys. J.

Calculation of transition probabilities and ac Stark shifts in two-photon laser transitions of antiprotonic helium

Numerical ab initio variational calculations of the transition probabilities and ac Stark shifts in two-photon transitions of antiprotonic helium atoms driven by two counter-propagating laser beams are presented. We found that sub-Doppler spectroscopy is in principle possible by exciting transitions of the type (n,L)->(n-2,L-2) between antiprotonic states of principal and angular momentum quantum numbers n~L-1~35, first by using highly monochromatic, nanosecond laser beams of intensities 10^4-10^5 W/cm^2, and then by tuning the virtual intermediate state close (e.g., within 10-20 GHz) to the real state (n-1,L-1) to enhance the nonlinear transition probability. We expect that ac Stark shifts of a few MHz or more will become an important source of systematic error at fractional precisions of better than a few parts in 10^9. These shifts can in principle be minimized and even canceled by selecting an optimum combination of laser intensities and frequencies. We simulated the resonance profiles of some two-photon transitions in the regions n=30-40 of the \bar{p}^4He^+ and \bar{p} ^3He^+ isotopes to find the best conditions that would allow this.Comment: 18 pages 2 tables 12 figures, submitted to Phys. Rev.

Tracking quasi-classical chaos in ultracold boson gases

We study the dynamics of a ultra-cold boson gas in a lattice submitted to a constant force. We track the route of the system towards chaos created by the many-body-induced nonlinearity and show that relevant information can be extracted from an experimentally accessible quantity, the gas mean position. The threshold nonlinearity for the appearance of chaotic behavior is deduced from KAM arguments and agrees with the value obtained by calculating the associated Lyapunov exponent.Comment: 4 pages, revtex4, submitted to PR

Quantum coherence generated by interference-induced state selectiveness

The relations between quantum coherence and quantum interference are discussed. A general method for generation of quantum coherence through interference-induced state selection is introduced and then applied to `simple' atomic systems under two-photon transitions, with applications in quantum optics and laser cooling.Comment: 17 pages, 7 figures, to be published in Journal of Modern Optics' special issue on quantum interferenc

Continuous spin reorientation in antiferromagnetic films

We study anisotropic antiferromagnetic one-layer films with dipolar and nearest-neighbor exchange interactions. We obtain a unified phase diagram as a function of effective uniaxial D_e and quadrupolar C anisotropy constants. We study in some detail how spins reorient continuously below a temperature T_s as T and D_e vary.Comment: 3 LaTeX pages, 3 eps figures. Submitted to JMMM on 25 May 2006. Accepted on 21 July 200